1. Field
This disclosure is directed to novel electrochromic materials and electrochromic devices fabricated using the electrochromic materials. More specifically, the electrochromic materials produce various colors and have bistability.
2. Description of the Related Art
Electrochromism is the phenomenon displayed by some chemical species wherein the species has a reversibly changeable color when a voltage is applied thereto. A material capable of undergoing reversible changes of optical properties such as color upon an electrochemical redox reaction is called an electrochromic material. The electrochromic material may not have a color in the absence of an electric field and then may display a certain color when an electric field is applied, for example, by an external source. Alternatively, the electrochromic material may have a color in the absence of an electric field and then may display no color when an electric field is applied.
Electrochromic devices taking advantage of such an electrochromic phenomenon have various advantages, such as high reflectivity without a need for an external light source, excellent flexibility and portability, and the possibility of weight reduction. Therefore, these electrochromic devices have promising applications for various flat-panel displays (“FPDs”). In particular, electrochromic devices are receiving a great deal of attention, due to high potential for use in E-paper, which is currently undergoing intense research and development as an electronic medium capable of replacing paper.
Examples of electrochromic materials include inorganic compounds such as tungsten oxides, molybdenum oxides, and the like, and organic compounds such as pyridine, aminoquinone and azine compounds. However, even though nano-electrochromic blue and green electrochromic materials are known, red electrochromic materials are not yet well developed.
In comparison with inorganic electrochromic materials, organic electrochromic materials have a disadvantage in terms of long-term stability, but have advantages in that they are applicable to flexible substrates and can be used to form thin films by wet processing. Based on these advantages, a great deal of research has been conducted on organic electrochromic materials.
Further, a combination of red, green and blue is required to achieve full-color electrochromic devices. However, few red electrochromic materials have been discovered to date. Under such circumstances, there exists a need to develop red electrochromic materials.